This description relates to a micro-mirror device and an array thereof. With recent advances in optical devices, various techniques which use light as a medium for inputting and outputting lots of information and for information transmission have been on the rise. Among them, there is a method of scanning beams emergent from a light source such as a barcode scanner or a scanning laser display.
Depending on the applications thereof, beam scanning techniques are required to vary in scanning speed and range. In conventional beam scanning techniques, various scanning speeds and ranges are achieved mainly by controlling the incident angle of beam with regard to a reflection facet of an operational mirror, such as a galvanic mirror or a rotating polygon mirror.
Indeed, a galvanic mirror is appropriate for applications that demand scanning speeds of several tens of hertz (Hz), while the polygon mirror can implement scanning speeds of several kilohertz (kHz).
According to the development of related technologies, extensive efforts have been made to apply beam scanning techniques to new devices or to improve the performance of the pre-existing devices having the beam scanning techniques applied thereto. Representative examples thereof include projection display systems, HMDs (head mounted displays) and laser printers.
In systems where the beam scanning technique of such a high spatial resolution is employed, a scanning mirror is generally provided for allowing a high scanning speed and a large angular displacement or a tilting angle.
With reference to FIG. 1, a conventional scanning apparatus employing a polygon mirror is schematically shown. In the scanning apparatus, as shown in FIG. 1, a beam emergent from a light source 10 travels through an optical unit 11 including various lenses and is reflected by a polygon mirror 12. As the polygon mirror 12 is rotated by a driving motor 13 formed underneath the polygon mirror 12, the incident beam can be scanned in the direction defined by the rotating direction (A) of the polygon mirror 12.
Generally, the polygon mirror 12 is usually mounted on the rotating motor 13 rotating at a high speed, so that the scanning speed depends on or proportional to the angular velocity of the polygon mirror 12.
As the scanning speed depends on or proportional to the rotational angular speed of the polygon mirror 12, a limited rotation speed of the motor leads to the limitation in increasing the scanning speed of the polygon mirror 12, resulting in difficulty or inadequacy for high resolution displays.
In addition, it is difficult to decrease the overall size of a system and the consumption of power due to the driving motor, which has fundamental problems of friction noise and contributes to an increase in production cost because of its complex structures. As one of the attempts to solve these problems, a micro mirror has been presented.
With reference to FIG. 2, a conventional scanning apparatus employing a micro mirror is schematically shown. In the scanning apparatus, as shown in FIG. 2, a beam emergent from a light source 20 travels through an optical unit 21 including various lenses and is reflected by a micro mirror 22.
In other words, a micro mirror 22 is rotated on torsion beam 23 as axes formed at both sides of the micro mirror 22 so that the beam incident on the micro mirror 22 can be scanned in the direction defined by the rotating direction (B) of the micro mirror 22.
As for the micro mirror 22, it allows a scanning apparatus to scan bi-directionally and at a high speed of tens of KHz, so that it is adequate for high resolution displays. However, if the micro mirror is driven at a high scanning speed under a harsh condition, as shown in FIG. 3, the micro mirror 22 is generated with a dynamic deflection to distort a reflection facet to result in the reflected beam being degraded.
The micro mirror 22 may be manufactured in various shapes depending on any particular application, and generally it comes and is used in the shape of a square, a rectangle, a circle, an oval and a lozenge. The micro mirror 22 shows various dynamic deflections according to its shape.
FIG. 5 is a graph illustrating a simulation of a dynamic deflection of a round micro mirror of FIG. 4, where the round micro mirror of FIG. 4 rotates to both directions about an axis defined by the torsion beams 28 to produce a dynamic deflection as illustrated in FIG. 5.